This is exactly my point - why do something so complicated when many people die quietly in their homes from CO poisoning? Let's just setup a CO poisoning chamber to do the same thing.

Or nitrogen as the article describes. Or a fatal overdose of a pleasant drug like morphine?

Even the guillotine is quite humane, though gory.

I never understood it either - there must be some crazy reason though.

Sadism, mostly. The electric chair was painful enough but too picturesque, which makes it easy to rally against. The injections solve that problem whilst still inflicting immense pain. Which is supposed to be good, because these damn criminals had it coming. Or something.

Many argue that the deliberate cruelty is the point. Also stigma around gas chambers.